Frozen food display chests are common, especially in supermarkets, and in order to cool this open-type of freezer chest circulating air is utilized having a moisture content which will gradually settle and form frost on the cooling elements in the air channels within the freezer chest. Consequently, these freezer chest units have to be defrosted at regular intervals in order to maintain their proper cooling effect. Thus, in order to achieve a rapid defrosting of freezer chests, electric heaters, for example, have been used, which are placed close to the cooling elements. The compressor is then shut down and heat energy is supplied to the heaters. The ventilating fans are kept in operation so that air circulation continues. In this manner a comparatively rapid defrosting of the cooling elements of a freezer chest is achieved, however at the same time considerable energy has to be supplied to the heaters, together with an expensive assembly of heaters with connecting wires. Therefore, in order to reduce or eliminate the supply of electric energy, it has been proposed to use heat from the atmosphere for heating the freezer chest. In order to achieve this objective special air channels have to be provided in the freezer chest for supplying warm air from the atmosphere and discharging the air cooled by the cooling elements so that there will be no air circulation. Thus, the construction becomes rather complicated because, not only additional air channels are required for defrosting, but also a system of movable flaps or guides is essential. The latter have to be adjusted before and after defrosting so that the desired air passages are created. Obviously, the above described defrosting devices involve an increased cost for the freezer chest and furthermore they add to the risk of operation interruption. In addition, the above-mentioned devices cause an increased need for supervision of the defrosting operation.
The present invention relates to an apparatus and method for defrosting cooling elements in an open-type freezer chest in which air is caused to circulate about frozen food items by means of a fan. The air flow additionally moves over the open side of the freezer chest.
A feature of the present invention is to provide defrosting of an open-type freezer display chest by relatively simple and reliable means, without any significant increase in cost, as well as rated input.
Another feature of this invention is that in the defrosting cycle the cooling elements are shut down and the air in the channel is caused to flow by means of fans in a direction opposite to its flow direction during normal operation. Thus, the air cooled by the cooling elements are caused by guides to flow out of the circulation path in a direction away from the frozen items. Furthermore, when this occurs, air from the ambient is drawn in at the place or places where air was previously blown out.
A further feature of the present invention is to provide an open-type freezer chest which has means for reversing the direction of air flow. Thus, upon defrosting, a discharge of air from the channel in the freezer chest is directed out of the circulation path and away from the frozen food items in the chest. When this occurs atmospheric air is drawn into the channel.